Why type instability?

[Steven_Sagaert]

@StefanKarpinski

Decades of empirical evidence indicate that numerical and scientific users just love to work in dynamic languages – Matlab, R, Python, Mathematica, SciLab, etc. The appetite to work in static languages is considerably more limited – people who really desperately need performance will use C++ and Fortran for scientific and numerical work, but they then almost immediately wrap their static code in a dynamic language.

Sure if static languages are C/C++/Fortran but modern languages like F# or Scala give you IMO the best of both worlds: flexibility , a repl for experimentation & (data) exploration, static type checking & AOT compilation, (reasonable) performance & high level code.